Preheat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners or lightly coat it with cooking spray.

Pulse the oats in a food processor or blender for about 30 seconds, until they look like coarse flour.

In a large bowl, whisk the melted butter and brown sugar together until smooth. Whisk in the pumpkin puree, milk, egg whites, and vanilla until well combined.

In a separate bowl, whisk together the ground oats, flour, salt, and baking soda. Add the dry ingredients to the pumpkin mixture and stir with a spatula just until no streaks of flour remain. Don't overmix.

Gently fold in the chocolate chips.

Divide the batter evenly among the muffin cups, filling each one nearly full. Sprinkle a few extra oats and chocolate chips on top, if you like.

Bake for 18 to 22 minutes, until the muffins are domed and a toothpick inserted in the center comes out clean or with just a few moist crumbs.

Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack. Serve warm or at room temperature.